Follicular Neoplasm of Thyroid: A Revisit to Current Differential Diagnosis and Molecular Testing Impact
The term "follicular neoplasm" was first used in the medical literature in 1891 by pathologist Virchow to describe a tumor with features of both an adenoma and a carcinoma.
(1). In 1942, another pathologist Hurtle proposed that these tumors be called "follicular adenomas with atypical cells"
(2). Then in 1953, when the first-ever fine needle aspiration (FNA) biopsy was performed on a follicular neoplasm, the term "follicular neoplasm" was again used to describe these tumors.
Differential diagnosis of a follicular neoplasm (FN) of the thyroid is based on clinical, histologic, and molecular features as well as imaging studies. The most important clinical feature is the presence of a thyroid nodule. FNs are typically solitary, round, or ovoid lesions that are well-circumscribed and range in size from a few millimeters to several centimeters. They may be solid or cystic and may contain areas of macrocalcification. FNs tend to be more common in women than men, and are usually found in middle-aged or older adults.
Histologically, FNs are characterized by the presence of papillary or follicular structures lined by epithelial cells that have one or more nuclear features suggestive of malignancy: nuclear enlargement, nuclear membrane irregularity, chromatin clearing, prominent nucleoli, and/or abnormal mitotic figures. These atypical cells can grow in a diffuse (“haphazard”) pattern or in a more organized fashion resembling normal follicles or papillae. In some cases, the neoplastic cells may form true follicles with an associated lumen filled with colloid material. The extent of tumor cell invasion into surrounding tissue can also vary considerably, from minimally invasive lesions confined to the thyroid gland to locally aggressive tumors that invade nearby structures such as the trachea or esophagus.
Molecular Testing and its Impact on FN DiagnosisMolecular testing is becoming increasingly important in the diagnosis of follicular neoplasm (FN). The most common molecular tests used to diagnose FN are thyroid-specific gene rearrangement tests, such as the RET/PTC and PAX8/PPARG tests. These tests can help distinguish between benign and malignant FNs. Additionally, immunohistochemistry (IHC) can be used to detect specific proteins that are overexpressed in FNs. IHC can also be used to identify certain genetic mutations that are associated with FNs. Molecular testing is not currently used to diagnose all FNs, but it is expected that more FNs will be diagnosed using molecular tests in the future.
There are a variety of molecular tests that can be performed on the follicular neoplasm of thyroid (FN) specimens to help guide diagnosis and treatment. The most common molecular test used in FN is the rearranged during transfection (RET) proto-oncogene mutation test, which can help distinguish between benign and malignant FNs. Other molecular tests that may be performed include the BRAF V600E mutation test, the PAX8/PPARG rearrangement test, and the RAS mutations test. Each of these tests has a different utility in diagnosing FNs, and your doctor will likely order one or more of these tests depending on the specific case.
Current Treatment Options
(3). The current World Health Organization (WHO) classification system for thyroid tumors was published in 2004 and it includes four main types of follicular neoplasms: benign follicular adenoma, Hurtle cell adenoma, follicular carcinoma, and Hurtle cell carcinoma.
(4). Benign follicular adenomas are the most common type of follicular neoplasm and they have an excellent prognosis with no risk of
Differential Diagnosis and Clinical Features of FN
Differential diagnosis of a follicular neoplasm (FN) of the thyroid is based on clinical, histologic, and molecular features as well as imaging studies. The most important clinical feature is the presence of a thyroid nodule. FNs are typically solitary, round, or ovoid lesions that are well-circumscribed and range in size from a few millimeters to several centimeters. They may be solid or cystic and may contain areas of macrocalcification. FNs tend to be more common in women than men, and are usually found in middle-aged or older adults.
Histologically, FNs are characterized by the presence of papillary or follicular structures lined by epithelial cells that have one or more nuclear features suggestive of malignancy: nuclear enlargement, nuclear membrane irregularity, chromatin clearing, prominent nucleoli, and/or abnormal mitotic figures. These atypical cells can grow in a diffuse (“haphazard”) pattern or in a more organized fashion resembling normal follicles or papillae. In some cases, the neoplastic cells may form true follicles with an associated lumen filled with colloid material. The extent of tumor cell invasion into surrounding tissue can also vary considerably, from minimally invasive lesions confined to the thyroid gland to locally aggressive tumors that invade nearby structures such as the trachea or esophagus.
Molecular Testing and its Impact on FN DiagnosisMolecular testing is becoming increasingly important in the diagnosis of follicular neoplasm (FN). The most common molecular tests used to diagnose FN are thyroid-specific gene rearrangement tests, such as the RET/PTC and PAX8/PPARG tests. These tests can help distinguish between benign and malignant FNs. Additionally, immunohistochemistry (IHC) can be used to detect specific proteins that are overexpressed in FNs. IHC can also be used to identify certain genetic mutations that are associated with FNs. Molecular testing is not currently used to diagnose all FNs, but it is expected that more FNs will be diagnosed using molecular tests in the future.
Current Molecular Testing Practices in FN of Thyroid
There are a variety of molecular tests that can be performed on the follicular neoplasm of thyroid (FN) specimens to help guide diagnosis and treatment. The most common molecular test used in FN is the rearranged during transfection (RET) proto-oncogene mutation test, which can help distinguish between benign and malignant FNs. Other molecular tests that may be performed include the BRAF V600E mutation test, the PAX8/PPARG rearrangement test, and the RAS mutations test. Each of these tests has a different utility in diagnosing FNs, and your doctor will likely order one or more of these tests depending on the specific case.
Current Treatment Options
The current standard of care for follicular neoplasm of the thyroid is the surgical removal of the tumor. However, there is still debate as to whether or not all patients with this diagnosis should undergo surgery. Some studies have shown that patients who are diagnosed with follicular neoplasm of the thyroid and have surgery have a lower risk of developing thyroid cancer than those who do not have surgery. Other studies, however, have not shown this same benefit.
There is still much unknown about the follicular neoplasm of the thyroid and more research needs to be done in order to determine the best course of treatment for all patients. In the meantime, patients should discuss all treatment options with their doctor and make a decision that is best for them.
There are two primary treatment strategies for follicular neoplasm of the thyroid (FNs), surgical resection and radiofrequency ablation (RFA).
Surgical resection is the most common treatment for FNs and involves the removal of the thyroid gland or a portion thereof. The extent of the surgery depends on the size and location of the tumor, as well as the patient's overall health. Radioactive iodine may also be used after surgery to destroy any remaining cancer cells.
RFA is a newer, less invasive treatment option that can be used in some cases of FNs. RFA uses high-frequency waves to heat and destroys cancer cells while sparing healthy tissue. This treatment is typically only an option for small tumors that have not spread beyond the thyroid gland.
Summary and Conclusions
There is still much unknown about the follicular neoplasm of the thyroid and more research needs to be done in order to determine the best course of treatment for all patients. In the meantime, patients should discuss all treatment options with their doctor and make a decision that is best for them.
Guidelines for Management of Follicular Neoplasms
The American Thyroid Association (ATA) has published guidelines for the management of follicular neoplasms of the thyroid gland. The guidelines are based on a comprehensive review of the available evidence and expert consensus.
The guidelines recommend that all patients with a follicular neoplasm should have surgery to remove the tumor. If the tumor is small (less than 1 cm in diameter) and there is no evidence of spread to other tissues, then surgery may be the only treatment necessary. For larger tumors, or those with evidence of spread, additional treatments such as radiation therapy or chemotherapy may be recommended.
Molecular testing can play an important role in the management of follicular neoplasms. The results of molecular tests can help doctors determine whether a tumor is benign or malignant and whether it is likely to respond to certain treatments. Molecular tests are generally not used to diagnose follicular neoplasms, but they may be useful in helping to make treatment decisions.
The Role of Interventional Radiology in FN
The guidelines recommend that all patients with a follicular neoplasm should have surgery to remove the tumor. If the tumor is small (less than 1 cm in diameter) and there is no evidence of spread to other tissues, then surgery may be the only treatment necessary. For larger tumors, or those with evidence of spread, additional treatments such as radiation therapy or chemotherapy may be recommended.
Molecular testing can play an important role in the management of follicular neoplasms. The results of molecular tests can help doctors determine whether a tumor is benign or malignant and whether it is likely to respond to certain treatments. Molecular tests are generally not used to diagnose follicular neoplasms, but they may be useful in helping to make treatment decisions.
The Role of Interventional Radiology in FN
Interventional radiology (IR) is a vital tool in the management of follicular neoplasm (FN). IR can be used to biopsy and stage FN, which are essential for deciding whether to pursue surgery or other treatments. Additionally, IR can be used to percutaneously ablate small thyroid nodules, which may be an alternative to surgery for some patients. In addition, IR can help guide fine-needle aspiration (FNA) of FN, which is the mainstay of diagnosis.
Molecular testing has improved our ability to diagnose and subclassify FN. The most important impact of molecular testing on IR is the identification of BRAF mutations, which are associated with a more aggressive clinical course. Patients with BRAF-mutant FN have a higher risk of recurrence and metastasis and should be managed with closer surveillance. Additionally, molecular testing can help guide FNA biopsy by identifying high-risk subsets of FN that may require more extensive sampling.
Molecular testing has improved our ability to diagnose and subclassify FN. The most important impact of molecular testing on IR is the identification of BRAF mutations, which are associated with a more aggressive clinical course. Patients with BRAF-mutant FN have a higher risk of recurrence and metastasis and should be managed with closer surveillance. Additionally, molecular testing can help guide FNA biopsy by identifying high-risk subsets of FN that may require more extensive sampling.
Treatment Strategies for FNs
There are two primary treatment strategies for follicular neoplasm of the thyroid (FNs), surgical resection and radiofrequency ablation (RFA).
Surgical resection is the most common treatment for FNs and involves the removal of the thyroid gland or a portion thereof. The extent of the surgery depends on the size and location of the tumor, as well as the patient's overall health. Radioactive iodine may also be used after surgery to destroy any remaining cancer cells.
RFA is a newer, less invasive treatment option that can be used in some cases of FNs. RFA uses high-frequency waves to heat and destroys cancer cells while sparing healthy tissue. This treatment is typically only an option for small tumors that have not spread beyond the thyroid gland.
Summary and Conclusions
The follicles of the thyroid produce these hormones.
Follicular neoplasm of the thyroid is a type of cancer that starts in the follicles of the thyroid gland. This article reviews the current understanding of follicular neoplasm of the thyroid and its differential diagnosis, as well as the impact of molecular testing on patient care.
Most cases of follicular neoplasm of the thyroid are benign (noncancerous). However, some cases can be malignant (cancerous). Benign tumors are usually not treated and have no impact on patient care. Malignant tumors may need to be treated with surgery, radiation therapy, or chemotherapy.
Molecular testing can help distinguish between benign and malignant tumors. It can also help guide treatment decisions. Molecular testing is becoming increasingly important as we learn more about the biology of cancer.
Follicular neoplasm of the thyroid is a type of cancer that starts in the follicles of the thyroid gland. This article reviews the current understanding of follicular neoplasm of the thyroid and its differential diagnosis, as well as the impact of molecular testing on patient care.
Most cases of follicular neoplasm of the thyroid are benign (noncancerous). However, some cases can be malignant (cancerous). Benign tumors are usually not treated and have no impact on patient care. Malignant tumors may need to be treated with surgery, radiation therapy, or chemotherapy.
Molecular testing can help distinguish between benign and malignant tumors. It can also help guide treatment decisions. Molecular testing is becoming increasingly important as we learn more about the biology of cancer.
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ANATOMICAL PATHOLOGY